Concun

CONCENTRATION UNITS
This handout will deal with units of concentration and how to convert from one concentration unit to another. It will be important tounderstand a few terms dealing with solutions, so let's define them:
Solution -- a mixture consisting of a solute and a solvent
Solute -- component of a solutionpresent in the lesser amount
Solvent -- component of a solution present in the greater amount
Concentration -- amount of a solute present in a solution per standardamount of solvent

There are numerous ways of expressing concentrations. It will be important to know the units used to express each concentration, as theseunits essentially define the concentration. Let's look at some ways to express concentration.

mass/mass Percent (m/m%): This unit of concentration is often usedfor concentrated solutions, typically acids and bases. If you were to look on a bottle of a concentrated acid or base solution the concentration expressed as aweigh/weight percent. A weight/weight percent is defined as:

Molarity (M): This unit of concentration relates the moles of solute per liter of solution.Parts per million (ppm): This unit of concentration may be expressed in a number of ways. It is often used to express the concentration of very dilute solutions. The"technical" definition of parts per million is:

Since the amount of solute relative to the amount of solvent is typically very small, the density of thesolution is to a first approximation the same as the density of the solvent. For this reason, parts per million may also be expressed in the following two ways: